1. Field of the Invention
The present invention relates to an apparatus for fabricating semiconductor devices, and more particularly, to an apparatus for performing chemical vapor deposition or oxidation/diffusion using a process tube.
2. Description of the Related Art
Low pressure chemical vapor deposition (LPCVD) equipment used for depositing films such as oxide films, nitride films, barium strontium titanate (BST) films and amorphous or polysilicon films on a semiconductor substrate, can be generally classified as a sheet-fed type or a batch type, the classification being based on the method of loading and processing wafers. Batch type LPCVD equipment loads a plurality of wafers on a boat of quartz, carries them into a process tube, and then forms a thin film at appropriate temperature and vacuum pressure while flowing a gas suitable for forming the thin film into the process tube.
LPCVD equipment includes a process tube formed of quartz, a process gas injection portion provided within the process tube, a waste gas exhaust portion for exhausting a process gas which is supplied from the process gas injection portion, a heating chamber for supplying heat to the process tube, a gas control system connected to the process gas injection portion, a vacuum pump connected to the waste gas exhaust portion, and a gas scrubber for scrubbing waste gas evacuated by the vacuum pump.
In typical LPCVD equipment that vertically loads wafers on a boat, the process gas injection portion is realized in the form of a gas nozzle within the process tube. Accordingly, a process gas flows into the process tube via a hole formed in the gas nozzle.
However, the process gas injection portion of the typical LPCVD described above has the following limitations. First, when a wafer of large diameter, for example, 300 mm, is processed, the deposition rate is too low, and thus the overall efficiency of the equipment is decreased. For example, the deposition rate of a polysilicon film is 12 xc3x85/min, and thus it takes a long processing time of about 14 hours to form a polysilicon film 10,000 xc3x85 thick. Accordingly, a bottle neck phenomenon occurs in the overall fabrication process. To prevent this bottle neck phenomenon and to increase the overall productivity in fabricating semiconductor devices, a large amount of redundant equipment is required.
When a particular film such as an oxide film containing impurities is formed, since the large amount of film formation gas such as SiH4 or PH3 is used, the gas container must be frequently replaced. In addition, the used amount of gas must be frequently checked so that the film formation gas does not run out during deposition of the film. Accordingly, for management, a large amount of human labor is required. The necessity for such a large amount of LPCVD equipment and human labor during the film deposition process increases the cost of fabrication and decreases competitiveness.
Second, when wafers of large diameter, for example, 300 mm, are processed, the film is less uniform, so resulting semiconductor devices formed on the wafers tend to be less reliable.
Third, during chemical vapor deposition, a non-reactant gas is adsorbed into a hole, through which a process gas is injected, so that a particle can be created. The size of the hole of a typical gas nozzle is 0.5-0.8 mm. A non-reactant gas is adsorbed around the hole of the gas nozzle forming extraneous matter in the form of a particle, while a process gas flows through the hole. Due to the extraneous matter in particle form, the gas nozzle should be replaced periodically. The extraneous particle matter may also fall on the semiconductor substrate, thereby causing various defects.
To address the above limitations, it is a first object of the present invention to provide a process tube for fabrication of semiconductor devices which increases the deposition rate, maintains the uniformity throughout a film, and prevents the formation of particles, when the film is formed on a wafer of large diameter.
It is a second object of the present invention to provide a semiconductor device fabrication apparatus including the process tube.
Accordingly, to achieve the first object of the invention, there is provided a process tube for fabrication of semiconductor devices, which includes a plurality of slit-type process gas injection portions for supplying process gas, each of the slit-type process gas injection portions being formed on an interior surface of each of a plurality of parallel recesses, which may be configured in the vertical direction, each recess being provided in the shape of a long and narrow depression on the inner surface of a first side of a cylindrical tube body having a predetermined thickness; and a plurality of waste gas exhaust portions for evacuating waste gas after performing a process, the waste gas exhaust portions being formed on a second side of the cylindrical tube body, which faces the process gas injection portions, in the vertical direction.
Preferably, the tube body includes a buffer gas pipe realized as a space formed within the first side along the circumference, the buffer gas pipe connecting with the process gas injection portions, and a gas exhaust pipe realized as a space formed within the second side along the circumference, the gas exhaust pipe connecting with the waste gas exhaust portions.
The buffer gas pipe is connected to a gas injection pipe, which is provided in the tube body, through a plurality of passages. Preferably, the gas injection pipe is connected to a gas control system pipe, and the gas exhaust pipe is connected to a vacuum pump pipe.
At least one process gas injection portion and at least one waste gas exhaust portion are formed on the first and second sides, respectively, of the tube body within an angle of 160 degrees in the circumferential direction. It is preferable that a plurality of process gas injection portions are formed at the center, left and right of the bottom of each recess, and a plurality of waste gas exhaust portions are formed to be spaced apart by a predetermined distance in order to prevent turbulence.
Preferably, the tope of the tube body is closed.
To achieve the second object of the invention, there is provided a semiconductor device fabrication apparatus including a process tube having a plurality of slit-type process gas injection portions for supplying process gas, each of the slit-type process gas injection portions being formed on an interior surface of each of a plurality of parallel recesses, which may be formed in the vertical direction, each recess being provided in the shape of a long and narrow depression on the inner surface of a first side of a cylindrical tube body having a predetermined thickness; and a plurality of waste gas exhaust portions for evacuating waste gas after performing a process, the waste gas exhaust portions being formed on a second side of the cylindrical tube body, which faces the process gas injection portions, in a vertical direction; a heating chamber for applying heat to the process tube from the outside of the process tube; a gas control system pipe for supplying gas to the process gas injection portions of the process tube; a vacuum pump pipe connected to the waste gas exhaust portions of the process tube; and a boat which is horizontally loaded with a plurality of wafers, the boat movable in and out of the process tube.
The semiconductor device fabrication apparatus is preferably low pressure chemical vapor deposition equipment or oxidation/diffusion equipment.
It is preferable that the boat rotates at a rate of 1-70 rpm/min during the deposition of a film, and the pitch between quartz plates on which wafers are mounted is 3.5-15 mm.
Preferably, the gas control system pipe is connected to the process gas injection portions through a gas injection pipe and a buffer gas exhaust pipe, which are formed in the process tube, and the pressure in the buffer gas exhaust pipe is 1-40 torr.
According to the present invention, slit-type process gas injection portions and hole-type waste gas exhaust portions are integrated with the inside of the process tube, thereby enhancing the function of supplying process gas into the process tube and the function of evacuating waste gas from the process tube. Consequently, the present invention can improve the deposition rate when a film is deposited on a wafer of large diameter.